Water on the Sun
What is the most curious place that you would expect to find water? We know it exists on the surface of our planet, in the atmosphere, also deep into the Earth in aquifers, even in ices on the Moon and Mars. It turns out, it also exists on our host star, the Sun! More specifically it is found in the dark and cooler areas of the Sun, the sunspots. The scientists were able to isolate spectra from those regions of around 3000 K temperature. The surrounding photosphere has a temperature of 5777K. There, water has already dissociated into ions and is not a molecule anymore, but only exists as free hydrogen (H) and hydroxyl (OH). But that is not the case in the sunspots. The water there may be superheated but its molecule rotates and vibrates absorbing energy. Each of these motions then contributes with various lines to the sunspots’ absorption spectra. For years the astronomers collected the sunspots spectra but could not decipher the information in them. In order to map the spectra of the superheated water in those extreme temperature conditions, scientists used theory, and specifically quantum calculations. Then they compared the observed absorption spectra of the solar spots to that of the theoretical calculations of water and found that the main features matched each other. Modern large databases of absorption lines in each frequency of the electromagnetic spectra allow for these comparisons. It is notable that we only know of the existence of superheated water in the Sun after many years of collecting spectral information and aided by the quantum theory tools that were not discovered but at the beginning of the 20th century.
Image credit: Sunspots in January 2014 and Earth size for comparison. Courtesy of NASA/SDO and the AIA, EVE, and HMI science teams
Source: Water on the Sun: The Sun yields more secrets to spectroscopy Jonathan Tennyson & Oleg L. Polyansky, Contemporary physics, Pages 283-294, 1998
Wikipedia, Solar photosphere